Tree shelters are open ended tubes that are placed over newly planted tree, sometimes natural regeneration or directly sown tree seed. Developed by Tuley while working for the Forestry Commission, Alice Holt, early field results lead to manufacturers producing vast numbers in a bewildering range of sizes, colours, types etc. A shelter can confer a number of protective functions as well as increasing establishment %'s. They can also accelerate the height growth of the young tree, at least until emergence from the top.
I spent much of my professional life carrying out research into their use and the effects they have on the young trees. :thumbup: